Included among the conventional internal gear manufacturing methods are those for cold-plastically forming gear teeth on an inner circumferential surface of a member press-formed into a cup shape by means of an internal gear forming die (for example, refer to Japanese Unexamined Patent Application Publication No. 1996-300083) and those for cutting gear teeth along an inner surface of a hollow member by press-inserting thereinto an internal gear tooth cutting chisel (for example, refer to Japanese Unexamined Patent Application Publication No. 2003-89015). Unfortunately, these conventional methods are not problem-free regarding precision and miniaturization. For example, when required to manufacture a miniaturized internal gear for use in precision devices, such as micro-geared motors that require high accuracy, the internal gear is manufactured from a resin capable of ensuring sufficient working accuracy but at the expense of hardness and strength.
To solve the above problem, proposals have been made for metallic glass internal gear manufacturing methods reliant on molten metal injection molding methods, such as die casting (Cf., e.g., International Publication Pamphlet No. 2005/024274).